docs: def Chisholm_Armand(x, rhol, rhog):
      r'''Calculates void fraction in two-phase flow according to the model
      presented in [1]_ based on that of [2]_ as shown in [3]_, [4]_, and [5]_.
  
      .. math::
          \alpha = \frac{\alpha_h}{\alpha_h + (1-\alpha_h)^{0.5}}
          
      Parameters
      ----------
      x : float
          Quality at the specific tube interval []
      rhol : float
          Density of the liquid [kg/m^3]
      rhog : float
          Density of the gas [kg/m^3]
  
      Returns
      -------
      alpha : float
          Void fraction (area of gas / total area of channel), [-]
  
      Notes
      -----
  
      Examples
      --------
      >>> Chisholm_Armand(.4, 800, 2.5)
      0.9357814394262114
  
      References
      ----------
      .. [1] Chisholm, Duncan. Two-Phase Flow in Pipelines and Heat Exchangers. 
         Institution of Chemical Engineers, 1983.
      .. [2] Armand, Aleksandr Aleksandrovich. The Resistance During the Movement
         of a Two-Phase System in Horizontal Pipes. Atomic Energy Research 
         Establishment, 1959.
      .. [3] Xu, Yu, and Xiande Fang. "Correlations of Void Fraction for Two-
         Phase Refrigerant Flow in Pipes." Applied Thermal Engineering 64, no. 
         1-2 (March 2014): 242–51. doi:10.1016/j.applthermaleng.2013.12.032. 
      .. [4] Dalkilic, A. S., S. Laohalertdecha, and S. Wongwises. "Effect of 
         Void Fraction Models on the Two-Phase Friction Factor of R134a during 
         Condensation in Vertical Downward Flow in a Smooth Tube." International 
         Communications in Heat and Mass Transfer 35, no. 8 (October 2008): 
         921-27. doi:10.1016/j.icheatmasstransfer.2008.04.001.
      .. [5] Woldesemayat, Melkamu A., and Afshin J. Ghajar. "Comparison of Void 
         Fraction Correlations for Different Flow Patterns in Horizontal and 
         Upward Inclined Pipes." International Journal of Multiphase Flow 33, 
         no. 4 (April 2007): 347-370. doi:10.1016/j.ijmultiphaseflow.2006.09.004.
      '''
      alpha_h = homogeneous(x, rhol, rhog)
      return alpha_h/(alpha_h + (1-alpha_h)**0.5)